1. Field of the Invention
The present invention relates to a non-volatile memory (NVM), and more particularly, to a non-volatile memory having one time programmable (OTP) memory cells.
2. Description of the Prior Art
As is well known, a non-volatile memory is able to continuously retain data after the supplied power is interrupted. Generally, after the non-volatile memory leaves the factory, the user may program the non-volatile memory in order to record data into the non-volatile memory.
According to the programming times limit, the non-volatile memories may be classified into a multi-time programmable (MTP) memory, a one time programmable (OTP) and a mask read only memory (Mask ROM). Generally, the MTP memory may be programmed many times, and the stored data of the MTP memory may be modified many times. On the contrary, the OTP memory may be programmed once. After the OTP memory is programmed, the stored data fails to be modified. Moreover, after the Mask ROM leaves the factory, all stored data has been recorded therein. The user is only able to read the stored data from the Mask ROM, but is unable to program the Mask ROM.
Moreover, depending on the characteristics, the OTP memories may be classified into two types, i.e. a fuse-type OTP memory and an antifuse-type OTP memory. Before a memory cell of the fuse-type OTP memory is programmed, the memory cell has a low-resistance storing state. After the memory cell of the fuse-type OTP memory is programmed, the memory cell has a high-resistance storing state. On the other hand, the memory cell of the antifuse-type OTP memory has the high-resistance storing state before being programmed, and the memory cell of the antifuse-type OTP memory has the low-resistance storing state after being programmed.
Generally, an OTP memory may comprise a plurality of OTP memory cells, and a shallow trench isolation (STI) structure may be used to isolate two adjacent OTP memory cells. However, the OTP memory may have too many STI structures that occupy the layout area of the OTP memory. Accordingly, the effective layout area for the OTP memory cells may be shrunk.